Conventional propel/repel lipstick dispensers typically have an outer helical cam track sleeve and a longitudinal track innerbody rotatable inside the cam sleeve to axially propel and retract an elevator cup with a lug or lugs that track in the cam track and in the longitudinal track.
It is known in the art to provide cosmetic dispensers such as lipstick cases with a desirable frictional drag "feel" to the consumer operator when the dispenser is operated to extend or retract the cosmetic stick. It is desirable in providing such a feel that the swivel torque needed to rotate the components to dispense the lipstick remain nearly constant, regardless of whether the dispenser is nearly full or exhausted of the cosmetic. The swivel torque should be significant enough to impart a firm feel to the dispenser. Looseness, uneven drag, or inconsistency of torque can be interpreted by the consumer as indicating an inferior quality product.
The prior art has attempted to provide the desired firmness and consistency of swivel torque by a number of devices. U.S. Pat. No. 4,750,501 to Ackermann et al. is an example of one type of cosmetic applicator wherein an objective is to impart an even drag and swivel torque during operation. In other prior art devices, two lugs or tabs are provided on the elevator cup to press against the innerbody or the cam sleeve to provide frictional interference therebetween; in other devices ribs have been provided on the innerbody that frictionally fit against the elevator cup. However, these prior art devices have generally suffered from inconsistent swivel torque along the travel of the elevator cup as it moves from the extended to the retracted position. This problem arises because the effective inner diameter of the innerbody can vary along its length and thereby vary the swivel torque in an undesirable manner. The dispenser can therefore tend to feel looser when the cup is at one end and tighter when the cup is at the other end.
In yet other prior art devices, two lugs or tabs are provided on the innerbody to press against the cam sleeve to provide frictional interference between the two rotating elements of the dispenser. Such a device is shown for example in U.S. Pat. No. 5,186,560, issued Feb. 16, 1993 to Holloway, the disclosure of which is hereby incorporated by reference, as well as in U.S. Pat. No. 5,186,561 issued Feb. 16, 1993 to Ackermann and Holloway, the disclosure of which is hereby incorporated by reference. It has been found that over long periods of time the resilient flex tabs can sometimes lose their frictional engagement with the cam sleeve. This is believed to be due to the use of a plastic material to form the innerbody. The plastic experiences "cold flow" from the force of the flex tab against the cam sleeve, so that the flex tab is eventually bent out of position. The bent flex tab will have a substantially reduced frictional engagement with the cam sleeve.
Another problem found in certain prior art dispensers is the problem of pomade back-off. Pomade back-off occurs when a consumer is using a lipstick dispenser and the force of applying the lipstick to the consumer's lips pushes the pomade and elevator cup down the helical tracks of the dispenser. Pomade back-off is generally prevented when the pomade is fully extended by providing horizontal locking tracks at the upper end of the inner body longitudinal tracks. However, if the consumer does not fully extend the pomade (as can often occur when a new lipstick is being used), the locking tracks are unavailing since the elevator cup is not extended sufficiently to engage in the locking tracks. Pomade back-off is most noticeable in single turn dispensers (in which the cam tracks extend around 360 degrees of the dispenser) which have relatively higher cam angles, so that pressure on the elevator cup tends to move the cup and pomade back down the cam and innerbody tracks. This problem is less acute in higher turn dispensers such as double or triple turn dispensers. However, for the convenience of a consumer, a single turn dispenser is preferable as it is easier and more elegant to use.